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HUBS191 ALEX > lecture 25 - homeostasis & hormones > Flashcards

lecture 25 - homeostasis & hormones Flashcards

1
Q

What are the 3 steps of the homeostatic mechanism?

A

Receptors detect change, control centre compares to set point and signals to effectors, effectors (organs/tissues) respond with localised or wide spread effects.

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2
Q

Why might a value for a characteristic be abnormal for an individual, even though it is inside the normal population range?

A

The population reference range is wider than the normal fluctuations found within an individual, because it contains the extremes of individuals within the population.

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3
Q

What are the differences between the neural and endocrine control systems?

A

Neural: fast, short lasting and highly targeted, Endocrine: slow, long lasting, targeted via specific receptors.

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4
Q

What are the major endocrine organs (studied in HUBS191)?

A

Hypothalamus, pituitary gland, adrenal gland, thyroid gland, pancreas, parathyroid glands.

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5
Q

What are some key physiological variables held in homeostasis by hormones?

A

Blood sugar concentration, growth & repair, basal metabolic rate, blood calcium concentration

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6
Q

What are hormone receptors?

A

Proteins found inside or in the plasma membrane of target cells that can bind to specific hormones.

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7
Q

What are water-soluble hormones typically made up of?

A

Peptides or catecholamines (e.g. adrenaline and noradrenaline)

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8
Q

What proportion of water-soluble hormones are peptides?

A

75%

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9
Q

What kind of receptors do water soluble hormones bind to?

A

Receptors on the surface of cells (within the cell membrane)

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10
Q

How are water-soluble hormones transported around the body?

A

Via the bloodstream, where they are dissolved into the blood.

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11
Q

Are water-soluble hormones stored?

A

Yes - stored until required, then released by exocytosis.

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12
Q

What is the process of cellular response to water-soluble hormone receptor activation?

A

Hormone binds to cell surface receptor, G protein is activated and activates or deactivates second messenger pathways that result in a cellular response.

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13
Q

What levels are controlled by water soluble hormones in a cell?

A

cAMP and Ca2+

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14
Q

What are key examples of lipid-soluble hormones?

A

Steroids, thyroid hormones

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15
Q

What are lipid soluble steroid hormones synthesised from?

A

steroids are made from cholestrol

Made when required (generally not stored) from cholesterol.

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16
Q

How do lipid-soluble hormones travel around the body?

A

In the bloodstream, bound to carrier proteins as they are insoluble in water.

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17
Q

Where are lipid-soluble hormone receptors found?

A

In the cytoplasm or nucleus of target cells.

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18
Q

How do lipid-soluble hormones enter target cells?

A

They arrive at the cell, dissociate from their carrier protein and diffuse across the phospholipid cell membrane.

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19
Q

What do lipid-soluble hormones receptor complexes act as?

A

Transcription factors, that bind to DNA to activate target genes.

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20
Q

**When target genes are activated by lipid-soluble hormone receptor complexes, what is produced?

A

transcription makes mRNA that can then be translated for protein synthesis.

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21
Q

How do lipid-soluble hormones lead to cellular responses?

A

The receptors facilitate gene activation, transcription and mRNA production, and then translation to produce proteins that have cellular effects.

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22
Q

Are the cellular effects of lipid-soluble hormones rapid or slow?

A

Slow - can take hours of days to synthesise proteins within the cell.

23
Q

What is the most common mechanism for maintaining hormone levels in the body?

A

Negative feedback

24
Q

How does negative feedback maintain hormone levels?

A

When the stimulus is removed and the change has been restored to normal, a feedback loop inhibits further release of the hormone.

25
Q

What is positive feedback in terms of hormone levels?

A

Amplification of a change, by releasing more and more hormones until the desired outcome is released, rather than trying to revert the body to the set point.

26
Q

What are blood hormone concentrations dependent on ?

A

Rate of hormone secretion, and rate of removal from the blood.

27
Q

How is removal of hormones from the blood regulated?

A

By enzymes or target cells

28
Q

What is the pancreas?

A

An organ, posterior to the stomach, which acts as an endocrine and exocrine gland

29
Q

In what way does the pancreas act as an exocrine gland?

A

Secretes digestive enzymes into the digestive tract, which is technically considered to be outside the body

30
Q

What part of the pancreas acts as an endocrine gland?

A

The pancreatic islets

31
Q

What proportion of the mass of the pancreas are taken up by pancreatic islets?

A

approx. 1%

32
Q

What are the hormones secreted by the pancreas?

A

Insulin and glucagon

33
Q

What cells secrete insulin?

A

Beta cells

34
Q

What cells secrete glucagon?

A

Alpha cells

35
Q

What is the role of the pancreatic hormones?

A

To regulate blood sugar levels

36
Q

What are the 2 metabolic states that the body is in, in terms of blood sugar concentration?

A

Fed and fasting states

37
Q

What is the fed state?

A

There is cellular uptake of nutrients & anabolic metabolism.

38
Q

What is anabolism?

A

Growth and building - synthesis of glycogen, protein and fat. Storing of energy

39
Q

What is the fasting state?

A

Mobilisation of nutrients and catabolic metabolism

40
Q

What is catabolism?

A

When the body breaks down food for energy - breakdown of glycogen, protein and fat

41
Q

What are the key target cells of insulin?

A

Muscle and adipose tissue cells, liver cells

42
Q

What stimulus causes the secretion of insulin?

A

Increasing blood glucose levels.

43
Q

What is the effect of insulin on liver cells?

A

Stimulates the liver to convert and store glucose as glycogen (glycogenesis). Fat is also synthesised.

44
Q

What is the effect of insulin on muscle and adipose tissue cells?

A

Increased glucose uptake/breakdown/cell respiration - fat is synthesised in adipose tissue. Increased amino acid uptake. Glycogen and protein synthesis in muscle.

45
Q

What is the primary function of glucagon?

A

To increase fuel release in response to low blood glucose concentration.

46
Q

What occurs in the liver in response to the release of glucagon?

A

Increased breakdown of glycogen to glucose (glycogenolysis), increased glucose synthesis (glucogenesis), increased ketone synthesis, increased breakdown of fat

47
Q

What is glycogenolysis?

A

The breakdown of glycogen into glucose by the liver

48
Q

What is gluconeogenesis?

A

The synthesis of glucose from non-carbohydrate sources

49
Q

What types of hormones are modified amino acids?

A

Catecholamines and thyroid hormones

50
Q

What types of hormones are able to be stored ready for release?

A

All water soluble (catecholamines and peptides) and modified amino acids (which includes catecholamines and thyroid hormones)

51
Q

What are steroid hormones?

A

Modified forms of cholesterol

52
Q

What is the difference between catecholamines in the nervous and endocrine system?

A

Catecholamines (e.g. epinephrine and norepinephrine) are used as synaptic neurotransmitters in the nervous system, but are transported via blood in the endocrine system. Some target cells can receive catecholamine signals via both systems.

53
Q

What tissues does glucagon act on?

A

Primarily the liver, but also adipose tissue.

54
Q

What is the overall effect of insulin on target cells throughout the body?

A

Increases their uptake of glucose.

HUBS191 ALEX (36 decks)

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